U.S. patent application number 10/944345 was filed with the patent office on 2005-05-05 for thin film magnetic head slider, magnetic head support mechanism, magnetic disk drive, and method of manufacturing magnetic head.
This patent application is currently assigned to Hitachi Global Storage Technologies Netherlands, B.V.. Invention is credited to Kohira, Hidekazu, Kurita, Masayuki, Shiramatsu, Toshiya, Soga, Masahiko, Tokuyama, Mikio.
Application Number | 20050094316 10/944345 |
Document ID | / |
Family ID | 34543840 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050094316 |
Kind Code |
A1 |
Shiramatsu, Toshiya ; et
al. |
May 5, 2005 |
Thin film magnetic head slider, magnetic head support mechanism,
magnetic disk drive, and method of manufacturing magnetic head
Abstract
A thermal flying height adjustment slider capable of being
mounted on a small-sized thin film magnetic head slider is provided
wherein terminals of an energizer serving as a heater prevent
corrosion of pole pieces and the number of terminals is reduced. In
one embodiment, one of terminals of the energizer serving as the
heater is electrically connected to the lower pole piece, so that a
relay terminal for a heating device is used also as the terminal
for preventing the corrosion of pole pieces.
Inventors: |
Shiramatsu, Toshiya;
(Ibaraki, JP) ; Kurita, Masayuki; (Ibaraki,
JP) ; Tokuyama, Mikio; (Ibaraki, JP) ; Kohira,
Hidekazu; (Kanagawa, JP) ; Soga, Masahiko;
(Kanagawa, JP) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Hitachi Global Storage Technologies
Netherlands, B.V.
AZ Amsterdam
NL
|
Family ID: |
34543840 |
Appl. No.: |
10/944345 |
Filed: |
September 17, 2004 |
Current U.S.
Class: |
360/234.5 ;
360/128; G9B/5.087; G9B/5.23 |
Current CPC
Class: |
Y10T 29/49032 20150115;
Y10T 29/49041 20150115; G11B 5/3133 20130101; G11B 5/607 20130101;
G11B 5/6064 20130101; Y10T 29/49046 20150115; G11B 5/6082 20130101;
G11B 5/6005 20130101 |
Class at
Publication: |
360/234.5 ;
360/128 |
International
Class: |
G11B 005/60 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2003 |
JP |
2003-369912 |
Claims
What is claimed is:
1. A thin film magnetic head slider to be used in such a fashion as
to face a magnetic recording medium during flying, comprising: a
slider substrate; a slider thin film stacked on the substrate; an
energizer formed between the slider substrate and the slider thin
film; a magnetic write device; and a magnetic read device; wherein
a terminal of the magnetic write device, a terminal of the magnetic
read device, and a terminal of the energizer are formed on an
outflow facet of the thin film magnetic head slider; and wherein
the terminal of the energizer is formed from a conductive material
having a higher standard electrode potential in a solution as
compared with potentials of the magnetic write device and the
magnetic read device, and is electrically connected to a lower pole
piece of the magnetic write device or a magnetic shield of the
magnetic read device.
2. A magnetic head support mechanism comprising the thin film
magnetic head slider according to claim 1.
3. A magnetic disk drive comprising the magnetic head support
mechanism according to claim 2.
4. The thin film magnetic head slider according to claim 1, wherein
the thin film magnetic head slider has a thickness ranging from
about 0.10 mm to about 0.23 mm.
5. A magnetic head support mechanism comprising the thin film
magnetic head slider according to claim 4.
6. A magnetic disk drive comprising the magnetic head support
mechanism according to claim 5.
7. The thin film magnetic head slider according to claim 1, wherein
the energizer is formed between an underlying insulation film
formed on the thin film magnetic head slider substrate and a lower
magnetic shield of the magnetic read device formed on the
underlying insulation film.
8. The thin film magnetic head slider according to claim 7, wherein
the thin film magnetic head slider has a thickness ranging from
about 0.10 mm to about 0.23 mm.
9. A magnetic head support mechanism comprising the thin film
magnetic head slider according to claim 8.
10. A magnetic disk drive comprising the magnetic head support
mechanism according to claim 9.
11. A thin film magnetic head slider to be attached and wired to a
suspension and used in such a fashion as to face a magnetic
recording medium during flying, comprising: a slider substrate; a
slider thin film stacked on the substrate; an energizer formed
between the slider substrate and the slider thin film; a magnetic
write device having a lower pole piece; and a magnetic read device;
wherein a terminal of the magnetic write device, a terminal of the
magnetic read device, and a terminal of the energizer are formed on
an outflow facet of the thin film magnetic head slider; and wherein
a relay terminal of the write device which is conductively
connected to the lower pole piece of the magnetic write device is
conductively connected to the wiring of the suspension and
connected to a ground.
12. A magnetic head support mechanism comprising the thin film
magnetic head slider according to claim 11.
13. A magnetic disk drive comprising the magnetic head support
mechanism according to claim 12.
14. The thin film magnetic head slider according to claim 11,
wherein the thin film magnetic head slider has a thickness ranging
from about 0.10 mm to about 0.23 mm.
15. A magnetic head support mechanism comprising the thin film
magnetic head slider according to claim 14.
16. A magnetic disk drive comprising the magnetic head support
mechanism according to claim 15.
17. A method of manufacturing a thin film magnetic head provided
with a thin film magnetic head slider, comprising: forming an
energizer on an insulating film formed on a substrate, forming an
insulating layer on the energizer, and forming internal metal films
withdrawn from the energizer; forming a lower shield film and a
lower gap film on the insulating layer and forming a magneto
resistive element (MR element) which is a magnetic read device and
a pair of electrodes for extracting a magnetic signal from the MR
element; forming an upper gap film, an upper shield film, and an
upper shield insulating film, forming a lower pole piece of a
magnetic write device on the upper shield insulating film, and
forming an internal metal film withdrawn from the lower pole and
conductively connecting one of the internal metal films withdrawn
from the energizer to the lower pole piece; forming a magnetic gap
film and an upper pole piece for the magnetic write device and
forming a coil and an insulating film, the coil being adaptive to
supply a current for generating a magnetic field on the upper pole
piece; forming a read line withdrawn from the electrode coupled to
the MR element and a write line withdrawn from the coil; forming a
protection insulating film; forming a write device terminal for
inputting a current externally to the coil and a read device
terminal for sending the magnetic signal out externally;
electrically connecting a terminal of the energizer to the lower
pole piece of the magnetic write device or the magnetic shield of
the magnetic read device; polishing and cleaning an air bearing
surface facing a magnetic recording medium; and performing
attachment and wiring of a suspension supporting the magnetic head
slider and cleaning; wherein the terminal of the energizer is
formed from a conductive material having a higher standard
electrode potential in a solution used for the polishing and the
cleaning as compared with potentials of the magnetic write device
and the magnetic read device, and an area of the terminal of the
energizer is made larger than a sectional area, on the air bearing
surface, of the lower pole piece or the upper pole piece of the
magnetic write device.
18. The method of manufacturing a thin film magnetic head according
to claim 17, wherein, in performing the attachment and wiring of a
suspension supporting the magnetic head slider and cleaning, the
terminal of the energizer is cleaned while being electrically
insulated from metallic components constituting the suspension
supporting the thin film magnetic head slider.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a thin film magnetic slider
for realizing high-recording density of a magnetic disk drive, a
magnetic head support mechanism, a magnetic disk drive, and a
method for manufacturing a magnetic head. In particular, the
invention relates to a flying height adjusting slider having a
function of adjusting a distance between a magnetic disk and a
magnetic head.
[0002] A known disk storage unit has a magnetic disk to be rotated
and a thin film magnetic head slider (hereinafter referred to as
"slider") which is positioned in a radial direction of the magnetic
disk. The slider has a recording/reproducing device and is
supported by a magnetic head support mechanism having a suspension.
The slider runs relatively above the magnetic disk to read and
write magnetic information from and to the magnetic disk. The
slider serves as an air lubricant bearing and flies owing to a
wedge film effect of air, so that the magnetic disk and the slider
are not brought into a direct solid contact with each other. In
order to realize the high recording density of the disk storage
unit and resulting larger capacity or downsizing of the storage
unit, it is desirable to increase a linear recording density by
reducing a distance between the slider and the magnetic disk, i.e.,
the slider flying height.
[0003] Conventionally, in designing the slider flying height, a
flying height margin has been provided in view of a variation in
processing, an air pressure difference depending on use
environment, a temperature difference depending on use environment,
and the like in order to prevent the contact of the slider with the
disk even under the worst conditions. If a slider that has a
function of adjusting a flying height for each head or for each use
environment is realized, the above margin can be eliminated.
Consequently, a flying height of the write/read device is largely
reduced while the slider can be prevented from coming into contact
with the disk. For example, in a known slider structure, a heating
device comprising a thin film resistor is provided in the vicinity
of write and read devices, and a part of a slider is heated as
required to thermally expand and protrude, thereby adjusting a
distance between the write and read devices and a magnetic
recording medium (see, for example, Japanese Patent Laid-open No.
5-20635 (page 3 and FIG. 1)).
[0004] Conventional sliders are provided with read relay terminals
for electrically connecting a magnetic read device to the external
and write device terminals for electrically connecting a magnetic
write device to the external. One of the sliders requires, in
addition to the read device terminals (two terminals) and the write
device terminals (two terminals), a pole corrosion prevention
terminal (one terminal) for suppressing corrosion of a magnetic
film in a solution during polishing and cleaning processes of a
production process (see, for example, Japanese Patent Laid-open No.
2003-77105 (page 3 and FIG. 1)). The number of terminals in the
slider requiring the pole corrosion prevention terminal is five in
total.
[0005] With the installation of another terminal for a heating
device which energizes and heats for the purpose of flying height
adjustment, a problem of difficult mounting has been detected. The
conventional slider has five terminals in total, namely, the write
device terminals, the read device terminals, and the pole corrosion
prevention terminal. In the case of adding the terminals for a
microthermal actuator used in the heating device for the flying
height adjustment, the number of terminals is increased to seven,
thereby making it difficult to mount them. Because a next
generation slider to which a thermal flying height adjustment
slider of the present invention is applied will be further
downsized, it will be even more difficult to mount seven terminals
on the slider.
[0006] Further, in the case where the seven terminals are mounted
on the slider, a region on which the pole corrosion prevention
terminal is mounted is inevitably assigned to a position near the
air bearing surface.
[0007] The known slider production process includes a polishing
process for shaping the air bearing surface and a cleaning process
for eliminating process residue. In this case, a protection
material which is provided near the terminal is scraped off due to
the polishing process, thereby undesirably exposing the pole
corrosion prevention terminal. Since a brush used in the cleaning
process for eliminating processing residue can often be charged,
there is a risk that the pole corrosion prevention terminal is
undesirably eroded due to charging at the time of contact with the
brush.
BRIEF SUMMARY OF THE INVENTION
[0008] Embodiments of the present invention reduce the number of
terminals of a thermal flying height adjusting slider which is
provided with a heating device for energizing and heating and to
enable the terminals to be mounted not only on a thin film magnetic
head of the conventional size but also on a next generation small
size thin film magnetic head.
[0009] In accordance with an aspect of the present invention, a
thin film magnetic head slider to be used in such a fashion as to
face a magnetic recording medium during flying comprises a slider
substrate; a slider thin film stacked on the substrate; an
energizer formed between the slider substrate and the slider thin
film; a magnetic write device; and a magnetic read device. A
terminal of the magnetic write device, a terminal of the magnetic
read device, and a terminal of the energizer are formed on an
outflow facet of the thin film magnetic head slider. The terminal
of the energizer is formed from a conductive material having a
higher standard electrode potential in a solution as compared with
those of the magnetic write device and the magnetic read device and
electrically connected to a lower pole piece of the magnetic write
device or a magnetic shield of the magnetic read device.
[0010] In some embodiments, the energizer is formed between an
underlying insulation film formed on the thin film magnetic head
slider substrate and a lower magnetic shield of the magnetic read
device formed on the underlying insulation film. Further, a relay
terminal of the write device that is conductively connected to the
lower pole piece of the magnetic write device is conductively
connected to the wiring of the suspension and connected to a
ground.
[0011] According to embodiments of the present invention, it is
possible to reduce the number of terminals by one, i.e., from seven
to six, by electrically connecting one of the terminals of the
heating device, i.e., the energizer, of the thermal flying height
adjusting slider to the lower pole piece or the shield to impart
the terminal a function of a pole corrosion prevention terminal.
Thus, it is possible to mount the terminals not only on the
conventional slider but also on the next generation small sized
slider, thereby enabling all the required electrical connections in
a limited area. Further, the grounding of the pole piece enables
prevention of a discharge between the slider and the disk otherwise
caused by static electricity accumulated on the slider during
flying, thereby achieving an effect of increasing reliability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagram showing a magnetic disk drive using a
magnetic head support mechanism on which a thin film magnetic head
slider of one embodiment of the invention is mounted.
[0013] FIG. 2 is a perspective view of the slider according to an
embodiment of the invention.
[0014] FIG. 3 is an end view showing the air outflow facet of the
slider according to the embodiment of the invention.
[0015] FIG. 4 is an enlarged cross-sectional view of the slider
according to the embodiment of the invention taken along line X-X
of FIG. 3.
[0016] FIG. 5 is an enlarged cross-sectional view of the slider
according to the embodiment of the invention taken along line Y-Y
of FIG. 3.
[0017] FIG. 6 is a flowchart showing a production process of the
thin film magnetic head and the magnetic disk drive according to an
embodiment of the invention.
[0018] FIG. 7 is a diagram illustrating a discharge prevention
structure.
[0019] FIG. 8 is a cross-sectional view taken along line Z-Z of
FIG. 3.
[0020] FIG. 9 is a flowchart showing a flying height inspection
method.
[0021] FIG. 10 is a flowchart showing a flying height adjustment
method.
[0022] FIG. 11 is a diagram showing a system constitution of the
magnetic disk drive according to an embodiment of the
invention.
[0023] FIG. 12 is an enlarged view of a coil of FIG. 2.
[0024] FIG. 13 is an enlarged view of a coil of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0025] A thin film magnetic head slider, a method of manufacturing
a thin film magnetic head using the slider, and a magnetic disk
drive having a magnetic head support mechanism using the slider,
according to embodiments of the present invention, will hereinafter
be described with reference to accompanying drawings.
[0026] Overall Magnetic Disk Drive
[0027] Shown in FIG. 1 is a schematic structure of a magnetic disk
drive 13 according to an embodiment of the invention.
[0028] The magnetic disk drive 13 includes a magnetic disk 10 and a
slider 1. The magnetic disk 10 stores magnetic information and is
rotated by a spindle motor. The slider 1 having a read/write device
mounted thereon is supported by a magnetic head support mechanism
(load beam) 15 having a suspension and positioned in a radial
direction of the magnetic disk. The slider reads and writes the
magnetic information from and to the magnetic disk while flying
relatively above the magnetic disk 10. The slider serves as an air
lubricant bearing and flies owing to an air wedge film effect, so
that the slider does not come into contact with the magnetic disk.
The slider faces the rotating magnetic disk to receive an air
stream at a rear end thereof. The rear end serves as an outflow
facet of the slider.
[0029] In order to realize a high recording density of the magnetic
disk drive and thus the increased capacity or downsizing of the
disk drive, it is desirable to increase a linear recording density
by reducing a distance between the slider 1 and the magnetic disk
10, i.e., a slider flying height. In recent years, the slider
flying height has been reduced to about 10 nm or less.
[0030] The slider 1 is attached to the plate spring like magnetic
head support mechanism (load beam) 15 having the suspension. The
slider 1 receives a pressing load from the magnetic head support
mechanism (load beam) toward a magnetic disk surface of disk 10.
The slider 1 together with the magnetic head support mechanism
(load beam) is allowed to seek in the radial direction of the
magnetic disk 10 by a voice coil motor 16 to write and read
information to and from the whole magnetic disk surface. The slider
1 retracts to a ramp 14 from the magnetic disk 10 while the disk
drive is not in operation or in the absence of read/write command
for a certain period of time.
[0031] While the disk drive having the load/unload mechanism is
described above, the similar effect of the invention is also
achieved in a disk storage unit of the contact start/stop type
wherein a slider waits at a specific region on a magnetic disk when
the disk drive is not in operation.
[0032] Slider
[0033] An enlarged view of the slider of FIG. 1 is shown in FIG. 2,
and an enlarged view of a coil unit of FIG. 2 is shown in FIG. 12.
The slider 1 includes a substrate (wafer) 1a and a thin film
magnetic head 1b. The substrate 1a is made from a typical material
such as a sintered body of alumina and titanium carbide
(hereinafter referred to as AlTiC). The thin film magnetic head 1b
includes a magnetic write device (upper portion of a part denoted
by numeral 2) and a magnetic read device (lower portion of the part
denoted by numeral 2) formed on the substrate 1a by thin film
processing; an internal metal film 3c serving as an outgoing line
which is in conductive contact with the magnetic write device and
the magnetic read device; write device terminals 4 for electrically
connecting the magnetic write device (the upper portion of the part
2) to the external; read device terminals 5 for electrically
connecting the magnetic read device (the lower portion of the part
2) to the external; an energizer 11 serving as a heating device for
adjusting a flying height of a read/write device by thermally
expanding and protruding a part of the slider by heating; internal
metal films 17 serving as outgoing lines which are in conductive
contact with the energizer 11 serving as the heating device; and
terminals 30 of the energizer for electrically connecting the
energizer 11 to the external.
[0034] A conventional slider is a substantial rectangular
parallelepiped having a length of 1.25 mm, a width of 1.0 mm, and a
thickness of 0.3 mm. In addition, the conventional slider has six
faces of an air bearing surface 6, an air inflow facet 7, an air
outflow facet 8, sides, and a back face. Incidentally, a next
generation small size slider is further downsized in progress so as
to improve positioning accuracy and reduce costs owing to mass
reduction. For example, the next generation small size slider has
the size of 70% of the conventional one, i.e., a length of 0.85 mm,
a width of 0.7 mm, and a thickness of 0.23 mm. Fine steps are
formed on the air bearing surface 6 by ion milling, etching, or
other processing. The slider serves as an air bearing for
supporting a load applied on its back face by generating an air
pressure when facing a disk (not shown). It has been confirmed that
the invention is applicable to a slider having a thickness of about
0.1 mm. Attachment and wiring are performed on the slider and the
suspension, which will be described in this specification. In this
case, the slider thickness of about 0.1 mm is sufficient to enable
provision of a terminal having a length of about 80 .mu.m on the
outflow facet of the slider in the formation of the terminals of
the suspension and the slider.
[0035] The air bearing surface 6 has the steps as described above
and can be divided in three faces which are substantially parallel
to one another. The three faces are a rail face 6a which is closest
to the disk, a shallow groove face 6b which is a step bearing face
recessed in a depth direction from the rail face by about 100 nm to
200 nm, and a deep groove face 6c which is recessed in the depth
direction from the rail face by about 1 .quadrature.m. When the air
stream caused by the disk's rotation enters the rail face 6a via
the shallow groove face 6b which is the step bearing, it is
compressed by the tapered passage to produce a positive air
pressure. In turn, when the air stream enters the deep groove face
6c via the rail face 6a or the shallow face 6b, it encounters the
broaden passage to produce a negative air pressure. Incidentally,
the depths of the grooves are exaggerated in FIG. 2.
[0036] The slider 1 is designed to fly in such a fashion as to make
a flying height at an air inflow end 7 larger than that at an air
outflow end 8. Accordingly, a distance between the air bearing
surface and the disk is smallest at a position near the air outflow
end. Since in the vicinity of the air outflow end the rail face 6a
protrudes toward the shallow groove face 6b and the deep groove
face 6c which surround the rail face 6a, a distance between the
rail face 6a and the disk becomes smallest unless the slider pitch
attitude and roll attitude are declined to a degree exceeding a
certain limit. The magnetic read/write device 2 is formed on a
region of the rail face 6a, the region belonging to the thin film
head 1b. The shape of the air bearing surface 6 is so designed as
to maintain a distance between the magnetic read/write device 2 and
the disk to an appropriate value, i.e., about 10 nm, by bringing
the load applied by the magnetic head support mechanism (load beam)
and the positive/negative air pressures generated on the air
bearing surface 6 into a good balance.
[0037] The above-described slider has the air bearing surface 6
which is the two-step bearing type air bearing surface consisting
of the three types of faces 6a, 6b, and 6c which are substantially
parallel to one another. However, the effect of the invention can
be achieved by using a slider having a step bearing type air
bearing surface consisting of four or more parallel faces.
[0038] Thin Film Head Structure
[0039] FIG. 3 is a view of the slider of FIG. 2 as viewed from the
air outflow end; FIG. 4 is an enlarged view of the thin film head
1b having the magnetic write device 2a and the magnetic read device
2b, showing a section taken along line X-X of FIG. 3; and FIG. 5 is
a sectional view taken along line Y-Y of FIG. 3. FIG. 13 is an
enlarged view of a coil shown in FIG. 3. This embodiment will be
described in detail with reference to FIGS. 2, 3, 4, and 5.
[0040] In the manufacturing processes of the magnetic head
manufacturing method according to an embodiment of the invention,
an underlying insulation film 9 is formed on the substrate 1a, and
then the energizer 11 formed from permalloy as an energizer serving
as a heating device is formed on the underlying insulation film 9.
In addition, an insulating layer 12 made from alumina or the like
is formed on the energizer 11. Then, the internal metal films 17
withdrawn from the energizer serving as the heater are formed. A
detailed description of the energizer serving as the heater will be
given later in this specification.
[0041] Next, a lower shield film 18, and a lower gap film 19 made
from alumina or the like, are formed on the insulating layer 12.
Then a magnetoresistive element 20 (hereinafter referred to as "MR
element"), which is the magnetic read device, and a pair of
electrodes 21 for extracting a magnetic signal of the MR element 20
are formed. Then, an upper gap film 22 made from alumina or the
like and an upper shield film 23 are formed, followed by forming an
upper shield insulating film 24 made from alumina or the like.
Then, a lower pole piece 25 of the magnetic write device is formed
on the upper shield insulating film 24, followed by forming the
internal metal film 3c withdrawn from the lower pole 25 to make
conductive connection with one of the internal metal films 17
withdrawn from the energizer 11 serving as the heating device to
the lower pole 25. Then, a magnetic gap film 26 made from alumina
or the like and an upper pole piece 27 of the magnetic write device
are formed. Next, a coil 28 for supplying a current for generating
a magnetic field on the upper pole piece 27 and an organic
insulating film 29 are formed. Then, read lines 3b withdrawn from
the electrodes 21 coupled to the MR element 20 and write lines 3a
withdrawn from the coil 28 are formed. Then, a protection
insulating film (slider thin film head) 1b made from alumina or the
like for protecting and insulating the thus-obtained components is
formed in such a fashion as to cover the overall components.
Lastly, write device terminals 4 for inputting a current externally
to the coil 28 and read device terminals 5 for sending the magnetic
signal to the external are formed. Simultaneously, terminals of the
energizer are formed. A material used for forming the terminals of
he energizer is a metal or a ceramic having a higher standard
electrode potential in a solution used in the later process steps
of polishing and cleaning the air bearing surface as compared with
a CoNiFe alloy which is a part of the materials used for forming
the lower pole piece 25 and the upper pole piece 27, such as Au,
Ag, Pt, Ru, Rh, Pd, Os, Ir, and like metals or a material (metal,
alloy, or compound, for example) selected from the group consisting
of conductive ceramics such as Al2O3TiC, SiC, TiC, WC, and B4C. The
terminals of the energizer serving as the heater are in conductive
contact with the pair of internal metal films 17 withdrawn from the
energizer with which the lower pole piece 25 is in conductive
contact via the internal metal film 3C, which input a current
externally to the energizer.
[0042] An area of each of the terminals 30 of the energizer is made
larger than a sectional area, on the air bearing surface, of the
lower pole piece 25 or the upper pole piece 27 of the magnetic
write device.
[0043] As described above, the lower pole piece 25 and the upper
pole piece 27 which must be prevented from being eroded in the
later process steps are brought into conductive contact with the
energizer terminals 30. The energizer terminals 30 has a potential
higher than the standard electrode potential in a solution of the
CoNiFe alloy, for example, which is part of the materials used for
the lower pole piece 25 and the upper lower piece 27. The above
conductive contact can cause a standard electrode potential in the
solution of the lower pole 25 and the upper pole 27 to shift to a
passive state region after the conduction with the energizer
terminals 30. Consequently, corrosion of the lower pole 25 and
upper pole 27 is suppressed. Thus, the energizer terminals 30
achieve an effect of preventing the corrosion of the pole
pieces.
[0044] Steps of the production process of the magnetic disk drive
of present embodiment will hereinafter be described with reference
to FIG. 6. As described above, a plurality of thin film magnetic
heads 1b are formed simultaneously on the slider substrate 1a (Step
101), and then the substrate 1a is cut into sticks by a machining
process (Step 102). Then, an air bearing surface 6 is formed by
polishing a cut surface of each of the bars (Step 103), followed by
cleaning (Step 104). A carbon protection film having a thickness of
a several nanometers is formed on the air bearing surface 6 so as
to prevent abrasion thereof even if the bearing surface 6 comes
into a short-time slight contact with a disk, as well as to prevent
corrosion of the thin film components in the air bearing surface
(step 105). A rail face 6a, a shallow groove face 6b, and a deep
groove face 6c of the air bearing surface are formed in order to
stabilize the slider (Step 106), and then the thin film magnetic
heads cut into sticks are cut into individual pieces (Step 107).
Another cleaning is performed (Step 108) to complete a thin film
magnetic head slider 1. After the completion, the slider is
attached to a suspension which is a part of a magnetic head support
mechanism, and then wiring assembly is performed (Step 109),
followed by another cleaning (Step 110). Lastly, the magnetic disk
drive is assembled (Step 111). It was confirmed that the terminals
30 of the energizer are preferably electrically insulated from,
i.e., not in a conductive connection with, a stainless steel
underlayer of the suspension in Step 110 by allowing the terminals
to float electrically. The reason for the insulation is that, when
the terminals 30 of the energizer, which are wiring connected to
the pole pieces, are in conductive connection with the stainless
steel, the different metals form a closed circuit when they contact
the solution to cause corrosion in some cases. Further, in a thin
film magnetic head wherein an upper shield film is used also as a
lower pole piece, the above effect is achieved by forming the
internal metal film 3c by withdrawing the internal metal film 3c
from the upper shield film in such a fashion as to conductively
contact with the upper shield.
[0045] Reason for Using Terminals of Energizer Serving as Heating
Device as Pole Corrosion Prevention Terminal
[0046] The terminals of the energizer are less harmful to the lower
pole piece even if they are electrically connected to the lower
pole as compared with the terminals of the write device and the
read device. The reasons for this advantage are as follows. No
charge is applied to the lower pole piece since the energizer
terminals are electrically connected to the earth in addition to
the lower pole; and, since it is possible to increase the thickness
of the insulating film between the shield and the energizer so as
to eliminate discharge between the energizer and the shield, the
read device is not influenced adversely by the connection between
the energizer and the lower pole piece. When the terminals of the
write device and the read device are connected to the lower pole in
order to impart thereto the corrosion prevention function, such
connection may cause application of charge to the pole piece and
the read device to deteriorate the read/write characteristics.
Therefore, the relay terminals of the heating device are most
suitably used as the relay terminals having the function of pole
corrosion prevention.
[0047] Grounding of One of Terminals of Energizer to be Used as
Heating Device
[0048] As described in the foregoing, the write device writes
magnetic information by generating a magnetic field between the
lower pole piece 25 and the upper pole piece 27 using the current
flowing the coil; therefore, it is necessary to prevent the current
to be input to the heating device 11 from being applied to the pole
pieces. Accordingly, it is necessary to connect one of the
terminals 30 of the energizer, to which the lower pole piece 25 is
conductively connected via the internal metal film 17 withdrawn
from the energizer serving as the heating device, to the ground via
the wiring of the suspension. By thus keeping a potential of the
pole forcibly at zero, discharge between the slider and the disk
due to static electricity accumulated on the slide during flying
can be prevented, producing an effect of increasing
reliability.
[0049] In another embodiment of the invention, a relay terminal for
preventing the charging of a head and the discharge to a disk is
provided on the slider without provision of the heating device for
flying height adjustment. Such a configuration is shown in FIG. 7.
A relay terminal for discharge prevention 31 is connected to the
lower pole piece 25 and the suspension wiring through a gold ball,
solder, or the like and grounded during operation to maintain a
potential of the pole piece at zero.
[0050] Energizer Serving as Heater
[0051] In the vicinity of the read/write device, the energizer 11
as a heater using a thin film resistor is formed by employing thin
film processing as shown in FIG. 4. In this embodiment, a thin line
made from permalloy and having a thickness of about 0.5 .mu.m and a
width of about 4.5 .mu.m is provided on a region having a depth of
about 60 .mu.m and a width of about 60 .mu.m in a meandering
manner. In addition, a gap is filled with alumina to form the
energizer which is the thin film resistor serving as the heater. A
resistance value is about 50 .OMEGA.. FIG. 8 is a cross-sectional
view of the energizer 11 as viewed from the outflow end, taken
along line Z-Z of FIG. 4.
[0052] Order of Terminals and Wirings
[0053] It is desirable to place the terminals of the energizer
serving as the heater on the center or edges of the slider from the
following reasons. The wiring from the six terminal for write/read
devices are bonded to a wiring pad formed on a suspension gimbal.
The wiring is divided into two sets in such a fashion that three
pieces of wiring pass on one of arms of the gimbal and the other
three pieces of wiring pass on the other arm of the gimbal. Then
the two sets of the wiring meet again to become six pieces of
wiring. The six pieces of wiring are routed around a root of the
suspension. In this case, the pieces of wiring having passed on the
center of the slider are placed at the outer part of the suspension
and the other pieces of wiring having passed on the edges of the
slider are placed on the center of the suspension. It is necessary
to reduce the wiring spacing when placing six pieces of wiring on a
region for four pieces of wiring, but, with such reduced wiring
spacing, the wiring can be influenced by noise during passing
through between the write current and the read current. In this
embodiment, since one of the terminals of the energizer serving as
the heater is conductively connected to the lower pole piece, it is
desirable to allow the wiring for the energizer to be less
susceptible to the effect of noise. Accordingly, the terminals of
the energizer are wired either on the center of the slider and the
outermost part of the suspension or on the ends of the slider and
the center of the suspension, thereby minimizing the possibility
that the pole piece is influenced by the noise.
[0054] Flying Height Adjustment Method
[0055] Hereinafter, a method of adjusting a flying height according
to one embodiment of the invention will be described.
[0056] A flying height adjustment procedure can generally be
divided into three steps: a step during designing, a step during
inspection before delivery, and a step during operation. In the
step during designing, a slider of the lower limit of variation is
designed to come into contact with a disk under the conditions of
the highest possible ambient temperature, the lowest possible air
pressure, and continuous writing. That is to say, the slider is
designed under the conditions of the conventional slider design
without flying height adjustment. A difference between the highest
ambient temperature and the lowest ambient temperature is
relatively large in a magnetic disk drive for mobile appliances. On
the other hand, a flying height is reduced relatively greatly due
to a thermal protrusion caused by heating of a magnetic pole during
continuous writing in a magnetic disk drive for servers. Thus, the
designing conditions vary depending on the appliance to be
used.
[0057] In the step during inspection before delivery, a flying
height of each of sliders is inspected and stored in a memory. The
method of inspecting the flying height is specifically shown in
FIG. 9. Since an amount of flying height adjustment is in
proportion to supplied power, power to be applied is initially set
to zero and then gradually increased until detection of contact of
the slider with the disk. The flying height of the slider is
calculated from the applied power at the time of the contact and
the coefficient of proportion between the amount of flying height
adjustment and the supplied power. A method of the detection of the
contact of the slider with the disk will be described later in this
specification. In addition, it is possible to further improve
accuracy of the flying height adjustment by storing not only a
difference between inner and outer peripheries but also the
variation in slider flying height.
[0058] In the step during operation, or basically in the case where
a client such as a computer issues a read/write command, power
corresponding to a flying height of the slider is supplied to a
selected active head. No power is supplied to the heads in an
idling state. The power to be supplied to the active head is
reduced in the case of continuous writing as well as of the highest
ambient temperature, and increased in the case of the lowest
ambient temperature by the use of the coefficient of proportion
between the amount of flying height adjustment and the supplied
power.
[0059] Simplest Basic Adjustment Algorithm
[0060] The basic control algorithm is shown in FIG. 10. A sensor
for measuring an air pressure and a temperature may additionally be
used in other methods, but, in the simplest control method, a
feedback control is performed so as to control power to be input to
the heating device only when a contact or an read error occurs.
This is because it is not problematic so far as conditions of no
contact (not in the state of a too short distance) in the state
where influences of the air pressure, the temperature, the
individual difference are input and no error (not in the state of a
too long distance) in reading magnetic information are satisfied.
In order to prevent the component from being damaged due to impact
of loading, it is effective to keep the flying height relatively
high without energizing the energizer serving as the heating device
when loading the slider above the disk, particularly when
activating the drive. A method of detecting the contact will be
described later in this specification.
[0061] The compensations for the flying height fluctuations caused
by the air pressure difference and the head individual difference
are performed only at the activation as shown in the drawing;
however, it is necessary to monitor the contact and the read error
at a predetermined interval or during operation in order to
compensate for the flying height fluctuation caused by the
temperature difference. Therefore, in the case of the magnetic disk
drive to be used in an appliance having a relatively large
temperature fluctuation during operation, it is effective to
compensate for the flying height fluctuation at a predetermined
interval or during operation.
[0062] Ambient temperature information can be obtained by a
temperature sensor that is an accessory of the drive, which makes
it possible to provide a flying height adjustment having a high
degree of accuracy.
[0063] Contact Detection Method
[0064] Known contact detection methods include (1) a method using
an acoustic emission (AE) sensor, (2) a method of monitoring
thermal asperity which is noise included in a read signal due to
heating by contact, and (3) a method of monitoring an off-track
signal (position error signal) which is generated when off-track
occurs due to slider's minute rotation about a pivot caused by
contact-frictional force.
[0065] The detection of the read error of magnetic information can
sufficiently be achieved by monitoring the so-called bit error
rate. It is difficult to monitor a write error unlike the read
error; however, since the flying height during writing is generally
lower than that caused during the reading by the expansion of the
device caused due to heating by the coil, the possibility of the
write error is low under the conditions where the read error does
not occur.
[0066] As another method relating to the flying height adjustment,
a method of observing in place a distance between the read device
and a medium by the use of amplitude of the read signals is known.
It is possible to apply this method to the detection method.
[0067] System Constitution
[0068] Shown in FIG. 11 is a system constitution of a disk storage
unit having the function of flying height adjustment according to
an embodiment of the invention. In this drawing, the energizer
serving as the heater is shown as a heating device.
[0069] It is to be understood that the above description is
intended to be illustrative and not restrictive. Many embodiments
will be apparent to those of skill in the art upon reviewing the
above description. The scope of the invention should, therefore, be
determined not with reference to the above description, but instead
should be determined with reference to the appended claims along
with their full scope of equivalents.
* * * * *